This invention relates to chucks, and in particular, to safety chucks mounted to equipment that processes web material such as sheets of film, paper, tissue, foil and the like.
During manufacturing and other operations, material may need to be mounted onto or off a roll. In conventional web treatments where machines handle reels of paper, plastics, metal foils, textiles and other sheet material, the cores of these reels must be mounted on the machines so that rotational drive can be selectively coupled to the cores to affect winding or unwinding of the web material entrained on the cores. The cores carrying the webs are normally tubular components. To affect the rotational drive to the core a shaft is generally inserted into and grips the core. Each end of the shaft then engages a chuck attached to a spindle rotationally attached to the machine.
The chucks are termed “safety” chucks when the chucks automatically grasp and close about the shaft ends and, when the machine starts rotating the spindles, prevent the roll from disengaging from the machine. Safety chucks generally are manually closed. If the machine starts with the safety chuck in an open position, prior art safety chucks employ a small sliding cam mechanism to close the safety chuck. These cam mechanisms are not very robust. After a few dozen to a hundred cycles, prior art cam mechanisms wear out. Another problem associated with prior art cam mechanisms is that the safety chuck is not completely closed. As the machine starts rotating, wear on the cam mechanism increases, thereby increasing the cumulative wear on the cam mechanism, shortening its life span.